Process for treating cassiterite ore

ABSTRACT

The present invention relates to a process for treating a cassiterite ore, characterized in that, just before the flotation operation, said ore is subjected to a preliminary flotation operation, using an amphoteric collector of formula: ##STR1## in which: R is R 1  or R 1  --O-- or ##STR2## R&#39; is H, CH 3 , polyoxyalkyl or R(CH 2 ) 3  or A q  --Z, R&#34; is H or A q  --Z 
     Ap and A q  are polymethylene chains, 
     Z is selected from the carboxylic, sulfonic or phosphonic groups.

The present invention relates to the enrichment of cassiterite ores byflotation by eliminating part of the gangue by means of an amphotericcollector.

Treatments of ores by flotation are known.

They are used for ensuring a concentration of the interesting ores bypartial or total separation of the elements constituting the gangue.

In a treatment of enrichment by flotation, the ore may be previouslyde-slimed (elimination of the fine particles, particularly the clays, bygranulometric cut), then, if necessary, the large elements are ground inorder to release the different mineral phases. Attrition may be added tothis preparation in order to improve the cleanness of the mineralsurfaces. To the mineral pulp thus formed is added a reagent, orcollector, which clings to the surface of the particles either of theinteresting species or of the undesirable species or gangue, renderingthe surface hydrophobic. By insufflating air, the air bubbles cling tothe hydrophobic surfaces and carry the particles over in the form offoam or froth representing the floated part. The species which has notretained any collector is not carried over in the froth.

The stability of the froth is generally ensured by adding to the mineralpulp so-called foaming reagents. When the form formed is excessive involume or too stable, it is sometimes envisaged to employ frothregulating agents.

In order to avoid (or to activate) fixation of a collector on one of themineral phases, other so-called depressing (or activating) reagents aresometimes added to the pulp, prior to the addition of the collector,which reagents cling selectively to the surface of the particles of oneof the mineral phases.

Froth flotation therefore generally comprises the series of thefollowing operations:

possible de-sliming

grinding and/or attrition

conditioning of the pulp with a depressing and/or activating agent

conditioning of the pulp with a collector

conditioning of the pulp with a foaming agent and/or a froth regulatingagent

insufflation of air.

Cassiterite is an oxide of tin which exists in ores in the state ofdeposit formations where the mineral is either already released orfinely scattered in a gangue.

In the first case, separation of the cassiterite is obtained bygravimetrical concentration treatments. In the second case, the ore isfirstly ground so as to release the cassiterite. The large fractions aregenerally subjected to a gravimetrical concentration, whilst thecassiterite present in the fine-grained ores may be recovered by directflotation. However, in the event of the ore containing sulfides, thelatter are previously removed, likewise by direct flotation of thesulfides.

For direct flotation of the fine-grained fractions of the ore,carboxylic, phosphonic and arsenic acids have been recommended ascollectors of the cassiterite, the latter acids presenting risks oftoxicity which are an obstacle to their use. At present, the use ofsulfosuccinamates is therefore preferred, as they ensure saferoperation. Their use as collectors of cassiterite is described inparticular in U.S. Pat. No. 3,469,693.

Minerals such as silicates and silico-aluminates (muscovite, chlorites,tourmaline, topaz, . . . ), fluorite, iron oxides and carbonates,particularly siderite, generally constitute a large part of the gangueof the cassiterite ores. The presence of these impurities considerablyhinders flotation of the cassiterite by reducing both the selectivityand yield of tin. The lack of selectively obtained brings about thenecessity of subjecting the concentrate of cassiterite to an additionaltreatment consisting either of a high-intensity magnetic separation oran acid lixiviation.

It has been found, and this represents the invention, that a substantialelimination of the undesirable impurities could be advantageouslyobtained by a preliminary flotation treatment using amphotericcollectors comprising at least one basic nitrogen and at least one acidgroup at the same time.

The collectors which may be used according to the invention are theproducts of formula: ##STR3## in which:

R may be R₁, --R₁ --O-- or ##STR4## where R₁ is a linear or branched,saturated or non-saturated alkyl radical, having 5 to 19 carbon atoms,or an alkylaryl radical, or a poly(oxyalkyl) radical; R₂ being H or CH₃,with the additional condition that R is a chain of lipophilic character,

R' may be H or CH₃ -- or poly(oxyalkyl) or R' is R--(CH₂)₃ -- or R' isA_(q) --Z,

R" is H or A_(q) --Z; in the case of n>1 there may be both substituentsH and substituents A_(q) --Z,

Ap and A_(q) are polymethylene chains containing respectively p and qcarbon atoms, p and q being integers from 1 to 4,

n is 0 or an integer from 1 to 5,

Z is a radical selected from the carboxylic, sulfonic or phosphonicgroups.

According to the invention, use may particularly be made of thecorresponding alkylaminopropionic, alkylaminopropylaminopropionic andalkoxypropylaminopropionic acids of formula:

    R--(NH--CH.sub.2 --CH.sub.2 --CH.sub.2).sub.n --NH--CH.sub.2 --CH.sub.2 --COOH

where R is CH₃ --(CH₂)_(m-1) or CH₃ (CH₂)_(m-1) O--CH₂ CH₂ CH₂ -- withm: 12 to 22, n=0, 1, 2 or 3

"Preliminary flotation" is understood to mean a flotation operationleading to the elimination of part (for example from 3 to 10% by weight)of the treated ore which is carried out on a product having undergonethe preliminary operations (de-sliming, grinding) and which, in theconventional process, would be subjected to flotation.

The invention will be more readily understood from the followingexamples.

In these tests, normal flotation was effected according to theconventional technique in two cells; the float of the first is retreatedin the second, yielding the final float and a non-float to berecirculated in the first cell where the non-float constitutes the finaltailings.

Preliminary flotation was carried out in one cell, the float whichcontains the undesirable elements being eliminated and the non-floatbeing taken up for supplying the normal flotation.

EXAMPLE 1

Treatment of a cassiterite ore containing, after elimination of thesulfides by flotation:

silicates

silico-aluminates (muscovite, chlorites, tourmaline)

carbonates (calcite, siderite)

fluorite

quartz

Conditions of flotation (nature and consumption of the reagents,expressed in grams per ton of ore supplying the flotation process):

    __________________________________________________________________________                            Preliminary flotation (according                                              to the invention)                                                             pH = natural pH 5.7                                                           N--alkylaminopropionic acid                                                   (alkyl being with copra chain) =                                              150 g/t                                                                       conditioning: 3 mins                                                          M.I.B.C. (methylisobutylcarbinol                                              20 g/t)                                               Normal flotation        Normal flotation                                      Sulfuric acid: 5 kg/t   Sulfuric acid: 2.7 kg/t                               pH = 2.4                pH = 2.4                                              Na.sub.2 SiF.sub.6 = 100 g/t                                                                          Na.sub.2 SiF.sub.6 = 100 g/t                                            depressant              depressant                          Na.sub.2 SiO.sub.3 = 200 g/t                                                                          Na.sub.2 SiO.sub.3 = 200 g/t                          Conditioning: 2 mins.   Conditioning: 2 mins                                  Tetrasodium sulfosuccinamate =                                                                        Tetrasodium sulfosuccinamate =                        300 g/t                 300 g/t                                               Conditioning: 3 mins.   Conditioning: 3 mins                                  M.I.B.C. = 40 g/t       M.I.B.C. =  45 g/t                                    __________________________________________________________________________

Results:

    __________________________________________________________________________               Without preliminary                                                                       With preliminary flotation                                        flotation   object of the invention                                           Yield       Yield                                                             in      Yield                                                                             in       Yield                                                    weight                                                                            %   in  weight                                                                             %   in                                                       %   tin tin %    tin tin                                           __________________________________________________________________________    Supply preliminary                                                                       --  --  --  100.0                                                                              1.87                                                                              100.0                                         flotation                                                                     Float      --  --  --  3.6  0.79                                                                              1.5                                           Supply cassiterite                                                                       100.0                                                                             1.87                                                                              100.0                                                                             96.4 1.91                                                                              98.5                                          flotation                                                                     Float (cassiterite                                                                       7.6 11.32                                                                             46.0                                                                              7.6  12.43                                                                             50.5                                          concentrate)                                                                  Non-float to be                                                                          14.7                                                                              4.34                                                                              34.1                                                                              15.4 4.07                                                                              33.5                                          recirculated                                                                  Final tailings                                                                           77.7                                                                              0.48                                                                              19.9                                                                              73.4 0.37                                                                              14.5                                          __________________________________________________________________________

EXAMPLES II AND III

The same ore is treated as in Example 1, the only differences comingfrom the use of various collectors according to the invention.

    __________________________________________________________________________    Example II                  Example III                                       __________________________________________________________________________    Preliminary                                                                         natural pH (6.6)      natural pH (6.6)                                  flotation                                                                           N--alkylaminopropionic                                                                              N--octyloxypropylaminopro-                        (accor-                                                                             acid (alkyl = radical pionic acid (alkyl = chain                        ding to the                                                                         of tallow chain) =    having 7/9 carbons) =                             invention                                                                           160 g/t               160 g/t                                                 Conditioning: 3 mins  Conditioning: 3 mins                                    M.I.B.C. = 10 g/t     M.I.B.C. = 10 g/t                                 Normal                                                                              Sulfuric acid:        Sulfuric acid: 2.8 kg/t                           flotation                                                                           2.7 kg/t                                                                      pH = 2.4              pH = 2.4                                                Na.sub.2 SiF.sub.6 = 100 g/t                                                                        Na.sub.2 SiF.sub.6 = 100 g/t                                          depressant                                                      Na.sub.2 SiO.sub.3 = 100 g/t                                                                        Na.sub.2 SiO.sub.3 = 100 g/t                            Tetrasodium sulfo-    Tetrasodium sulfosuccinate =                            succinate = 300 g/t   300 g/t                                                 Conditioning: 3 mins  Conditioning: 3 mins                                    M.I.B.C. = 40 g/t     M.I.B.C. = 40 g/t                                 __________________________________________________________________________

Results:

    __________________________________________________________________________                Preliminary flotation                                                                       Preliminary flotation                                           with N--alkylaminopropio-                                                                   with N--octyloxypropyl-                                         nic acid (alkyl = tallow)                                                                   aminopropionic acid                                             Yield         Yield                                                           in       Yield                                                                              in      Yield                                                   weight                                                                             %   in   weight                                                                            %   in                                                      %    tin tin  %   tin tin                                         __________________________________________________________________________    Supply preliminary                                                                        100.0                                                                              1.86                                                                              100.0                                                                              100.0                                                                             1.87                                                                              100.0                                       flotation                                                                     Float       2.3  0.68                                                                              0.8  1.9 0.79                                                                              0.8                                         Supply cassiterite                                                                        97.7 1.87                                                                              99.2 98.1                                                                              1.89                                                                              99.2                                        flotation                                                                     Float (cassiterite                                                                        7.6  12.26                                                                             50.1 7.7 12.63                                                                             52.0                                        concentrate)                                                                  Non-float to be recircu-                                                                  15.9 3.33                                                                              30.4 17.8                                                                              3.20                                                                              30.5                                        lated                                                                         Final tailings                                                                            74.2 0.47                                                                              18.7 72.6                                                                              0.43                                                                              16.7                                        __________________________________________________________________________

EXAMPLE IV

Treatment of the same ore using as collector of normal flotationstyrenephosphonic acid instead of tetrasodium sulfosuccinamate.

Conditions of flotation (nature and consumption of the reagents,expressed in grams per ton of ore supplying the flotation process):

    ______________________________________                                                       Preliminary flotation                                                         (according to the invention)                                                  pH = natural pH 5.8                                                           N--alkylaminopropionic acid (alkyl                                            being with copra chain = 160 g/t                                              Conditioning: 3 mins                                                          M.I.B.C.:10 g/t                                                Normal flotation                                                                             Normal flotation                                               Sulfuric acid: 1.1 kg/t                                                                      Sulfuric acid: 0.7 kg/t                                        pH = 4.5       pH = 4.5                                                       Styrenesphosphonic acid =                                                                    Styrenephosphonic acid =                                       390 g/t        390 g/t                                                        Conditioning: 3 mins                                                                         Conditioning: 3 mins                                           M.I.B.C. = 35 g/t                                                                            M.I.B.C. = 35 g/t                                              ______________________________________                                    

Results:

    __________________________________________________________________________               Without preliminary                                                                       With preliminary flotation                                        flotation   object of the invention                                           Yield                                                                         in      Yield                                                                             Yield in Yield                                                    weight                                                                            %   in  weight                                                                             %   in                                                       %   tin tin %    tin tin                                           __________________________________________________________________________    Supply preliminary                                                                       --  --  --  100.0                                                                              1.89                                                                              100.0                                         flotation                                                                     Float      --  --  --  5.1  1.12                                                                              3.0                                           Supply cassiterite                                                                       100.0                                                                             1.84                                                                              100.0                                                                             94.9 1.93                                                                              97.0                                          flotation                                                                     Float (cassiterite                                                                       7.8 8.67                                                                              36.6                                                                              6.3  11.79                                                                             39.3                                          concentrate)                                                                  Non-float to be                                                                          16.9                                                                              3.98                                                                              36.6                                                                              14.8 4.84                                                                              37.9                                          recirculated                                                                  Final tailings                                                                           75.3                                                                              0.65                                                                              26.6                                                                              73.8 0.51                                                                              19.8                                          __________________________________________________________________________

EXAMPLE V

Treatment of another cassitierite ore containing:

silicates

silico-aluminates (muscovite, chlorites, tourmaline)

carbonates (calcite, siderite)

fluorite

quartz

Conditions of flotation (nature and consumption of the reagentsexpressed in grams per ton of ore supplying the flotation process):

    __________________________________________________________________________                            Preliminary flotation                                                         (according to the invention                                                   pH = natural pH 6.5)                                                          N--alkylaminopropionic acid (alkyl                                            being with copra chain) = 250 g/t                                             Conditioning: 3 mins                                  Normal flotation        Normal flotation                                      Sulfuric acid: 3.5 kg/t Sulfuric acid: 2.3 kg/t                               pH: 2.4                 pH: 2.3                                               Na.sub.2 SiF.sub.6 : 100 g/t                                                                          Na.sub.2 SiF.sub.6 : 100 g/t                                            depressant               depressant                         Na.sub.2 SiO.sub.3 : 200 g/t                                                                          Na.sub.2 SiO.sub.3 : 200 g/t                          Conditioning: 2 mins    Conditioning: 2 mins                                  Tetrasodium sulfosuccinamate =                                                                        Tetrasodium sulfosuccinamate =                        300 g/t                 300 g/t                                               Conditioning: 3 mins    Conditioning: 3 mins                                  M.I.B.C. = 45 g/t       M.I.B.C. = 50 g/t                                     __________________________________________________________________________

Results:

    __________________________________________________________________________               Without preliminary                                                                       With preliminary flotation                                        flotation   object of the invention                                           Yield       Yield                                                             in      Yield                                                                             in       Yield                                                    weight                                                                            %   in  weight                                                                             %   in                                                       %   tin tin %    tin tin                                           __________________________________________________________________________    Supply preliminary                                                                       --  --  --  100.0                                                                              1.36                                                                              100.0                                         flotation                                                                     Float      --  --  --  9.0  0.87                                                                              5.7                                           Supply cassiterite                                                                       100.0                                                                             1.40                                                                              100.0                                                                             91.0 1.41                                                                              94.3                                          flotation                                                                     Float (cassiterite                                                                       5.7 6.79                                                                              27.5                                                                              5.5  12.12                                                                             49.0                                          concentrate)                                                                  Non-float to be                                                                          25.3                                                                              2.91                                                                              52.4                                                                              24.4 2.07                                                                              37.1                                          recirculated                                                                  Final tailings                                                                           69.0                                                                              0.41                                                                              20.1                                                                              61.1 0.18                                                                              8.2                                           __________________________________________________________________________

The preliminary flotation treatment by means of the collectors accordingto the invention makes it possible to obtain a significant improvementin selectivity in the course of the subsequent direct flotation of thecassiterite whilst substantially reducing the consumption of acidnecessary for maintaining the pH of the flotation (in addition, theresidual presence of the amphoteric collector avoids obtaining aconsiderable volume of very stable froth inherent in the flotation ofthe cassiterite with the aid of sulfosuccinamates).

What is claimed is:
 1. A process for the preliminary flotation of acassiterite ore in order to recover impurities selected from the groupconsisting of silicates, silicoaluminates, fluorite, iron oxides andcarbonates in the float and provide an improvement in selectivity in thecourse of subsequent concentrations of said ore by anionic flotation,comprising the step of effecting flotation by means of an amphotericcollector of the formula:

    R--(NH--CH.sub.2 --CH.sub.2).sub.n --NH--CH.sub.2 --CH.sub.2 --COOH

in which: R is CH₃ --(CH₂)_(m-1) or CH₃ --(CH₂)_(m-1) OCH₂ CH₂ CH₂ --, mis 12 to 22, and n is 0, 1, 2, or
 3. 2. The process according to claim 1wherein the collector is N-octyloxypropylaminopropionic acid.
 3. Theprocess according to claim 1, wherein the collector isN-alkylaminopropionic acid.
 4. The process according to claim 3 whereinthe alkyl group is a copra alkyl group.
 5. The process according toclaim 3 wherein the alkyl group is a tallow alkyl group.